territorial aggression?

So, Cassie has lunged at me a couple of times. It seems to me that she was claiming the litter box as hers and was warning me away (she runs away and jumps in the box or upstairs - it's obvious she wants me to leave her alone). It was just a little stomp forward which gave me a fright, but I googled it. From what somebody else commented in answer to another of my (endless) questions, I figured I shouldn't let her "call the shots" so I insisted on the pat and she submitted. It was fairly half-hearted in terms of aggression (assuming that's what it was). Is that the right way to go with this? Just tell her it's fine, and she's getting patted and carry on with what you want? When she lunges, is there a chance she'll bite me? When do I need to be worried? I can tell with a dog, but I don't know bunnies (yet!)

She's getting spayed on Monday, and I've only just got them and we're working on our relationship, so I'm not too concerned, just trying to learn. Thanks.